About 20 million Americans have chronic kidney disease while an additional 20 million are at risk. Glomerular Filtration Rate (GFR) is one of the best indexes of kidney function. It is determined by measuring the rate of disappearance of certain markers from blood and their appearance in the urine. Currently used methods for measuring the GFR are either expensive, difficult, or require radioactive markers, and specialized facility and trained personnel. Thus, there is a great need to develop a convenient and rapid method for GFR measurement that does not require use of radioactive markers, is accurate and costeffective. In order to satisfy this need, Lynntech is proposing the development of a simple device to measure GFR using non-radioactive iodinated markers such as iothalamate. This device is based on an innovative method that combines electrochemistry, solid phase extraction (SPE) and colorimetry. During Phase I of this project, Lynntech will investigate the feasibility of using this innovative combination of electrochemistry in conjunction with SPE and colorimetry for accurate determination of GFR. This method will be tested with blood/serum and urine samples and the results compared to that obtained using standard HPLC method for determination of the GFR markers at Indiana University. The optimized conditions obtained during the Phase I will be used for designing, fabricating and testing of a prototype device for rapid and accurate measurement of GFR during Phase II.